This invention relates to a method to detect the bright-band snow level in near real time from radar reflectivity and Doppler vertical velocity data collected with an atmospheric profiling Doppler radar.
Portions of the present invention were disclosed in an extended abstract accompanying a presentation at the 30th International Conference of Radar Meteorology in Munich, Germany, Jul. 19-24, 2001. This abstract was published by the American Meteorological Society of Boston, Mass. on Jul. 1, 2001.
The bright band is a layer of enhanced radar reflectivity resulting from the difference in the dielectric factor for ice and water and the aggregation of ice particles particles as the particles descend and melt. The bright-band height is the altitude of maximum radar reflectivity in the bright band. The layer over which the transformation from ice to water occurs defines the melting layer. The top of the melting layer is the melting level. The melting level is commonly accepted as the altitude of the 0xc2x0 C. constant-temperature surface (see reference, Glickman, 2000, entitled Glossary of Meteorology, AMS, Boston, page 482).
Knowledge of the melting layer is extremely useful to the weather forecast community. One use is to predict and monitor the snow level defined as the lowest level in the atmosphere where snow or ice completely changes to rain. This is in contrast to the surface elevation where snow or ice accumulates on the ground. The snow level coincides with the bottom of the melting layer. Present known methods do not permit the snow level detection using direct or indirect measurement techniques. The bright band height can be measured directly and routinely using Doppler radar and provides a better estimate of the snow level than the melting level because of the time required for snow to melt at temperatures above freezing. The term bright band snow level or BBSL is used herein, rather than simply bright band height, to give the measurement a better meteorological context and to emphasize that the term applies not only to radar meteorology, but to other disciplines, such as weather forecasting.
Devices that can be used to measure relationships using radar reflectivity or the like known in the prior art. For example, in U.S. Pat. No. 4,014,019 to Fetter discloses a system for processing the IF portion of a radar return signal to produce a continuous voltage output which is indicative of velocity of precipitation in the radar target range.
U.S. Pat. No. 5,406,481 to Shinozawa et al discloses an apparatus for providing a short time range forecast with relatively high accuracy from weather radar images of cloud reflections data by incorporating physical properties of the cloud in the forecasting method.
U.S. Pat. No. 6,081,221 to Zrnic et al discloses a method of resolving range ambiguities and separating overlaid signals in a Doppler weather radar in which signals are decoded from one range interval, and made coherent, while the signal from the other range interval has a multiple split spectrum.
U.S. Pat. No. 6,125,328 to Baron et al discloses an improved system for obtaining data from the NEXRAD system.
U.S. Pat. No. 6,252,539 to Philips et al discloses a method for automatically generating weather alerts by collecting data to detect the presence of storm cells, their direction, location and speed.
The present invention is directed to a method to detect the bright band snow level in near real time from radar reflectivity and Doppler vertical velocity data collected with an atmospheric profiling Doppler radar.
This invention relates to a method to detect the bright-band snow level from radar reflectivity and Doppler vertical velocity data with an atmospheric profiling Doppler radar. The measurement may be made available to the public through the internet.
It is the primary object of the present invention to provide for an improved method to detect bright-band snow level in the atmosphere.
Another object is to provide for such a method using radar reflectivity and Doppler vertical velocity data.
These and other objects and advantages of the present invention will become apparent to readers from a consideration of the ensuing description and the accompanying drawings.